DE 10 2008 015 853 A1 discloses a method for producing a heatable plastic window for motor vehicles with at least one plastic layer, wherein at least one heat conductor is printed onto the inner side of the plastic layer, preferably in a 3D screen-printing process. In this method, the plastic layer is made available in the form of a film, a sheet or an injection-moulded part. In order to print on the heat conductor, a monofilament polyester fabric is used as screen-printing fabric and an electrically conductive paste with metal particles, preferably silver particles, is used as screen-printing ink. After the heat conductor has been printed on, the plastic layer is heat-treated and/or deformed. The 3D screen-printing process is carried out on a curved surface on the inner side of the plastic layer, wherein two bus bars (principal heat conductors) are laterally arranged on the right and the left side of the plastic window and several grid lines (branch heat conductors), which are electrically connected to the two bus bars, horizontally extend essentially in a straight line and parallel to one another. The plastic layer of the plastic window is essentially made of polycarbonate, polymethylmethacrylate, polymethylmethacrylimide or cycloolefin copolymers.
Conventional screen-printing devices are suitable for printing plane objects such as, e.g., plane car window panes, wherein the strip conductors of a rear-window defroster are applied onto a plane car window pane, e.g., by means of screen printing. After the strip conductors have been printed on, the window pane is heated and bent while the ink printed on simultaneously cures.
A squeegee with an elastic application element and a holding device for screen-printing arbitrarily curved surfaces is disclosed in DE 103 44 023 B4, wherein the holding device is viewed over the width of the squeegee divided into several holding sections that can be moved relative to one another and a guide plate, which rests against the application element at least during the printing process, originates from each holding section. Due to the division into several holding sections that can be moved relative to one another, the squeegee can be adapted to differently curved surfaces of an object to be printed. The guide plates furthermore ensure a uniform pressure distribution over the pressing edge of the application element.
Furthermore, DE 103 62 093 B4 discloses a screen-printing method for printing curved surfaces with the following steps: reading in a surface contour of an object to be printed, storing the read-in surface structure in a central control unit, generating control commands by means of the control unit and aligning a printing unit during the printing process by means of actuators that are activated by the control commands as a function of the surface geometry of the object to be printed, as well as the position of the squeegees relative to the object to be printed, and thereby constantly holding a printing unit frame relative to the object to be printed during a printing motion of the squeegees in an imaginary contact line between squeegee and the object to be printed.